The ssRMP will have a section in it relating to each of the Management Units in your scheme. A Management Unit is a field or group of fields managed together as one unit, for example a group of fields grazed together is a management unit.
You will need to plan your stocking rate for each of the Management Units in your agreement.
EFS(H) Stocking Rate checker tool revised 2020
Instruction for Stocking rate checker tool and example for mosaic calculator – revised 2020